The present disclosure relates to a method and apparatus for scheduling user equipments based on levels thereof in a mobile communication system. More particularly, the present disclosure relates to a method and apparatus that apply proportional fair scheduling to determine scheduling priorities of user equipments (UEs) in consideration of both UE channel states and UE categories or capabilities in a packet-based mobile communication system.
In a packet-based mobile communication system such as the High Speed Downlink Packet Access (HSDPA) system, radio resources are allocated differently to UEs according to services requested by the UEs. Although users wish to receive various services at high speed, as radio resources are limited in the packet-based mobile communication system, the UEs have to compete with each other for radio resources. For efficient allocation of radio resources, scheduling priorities may be applied to UEs and services. For example, for each unit time (e.g. Transmission Time Interval (TTI)), resources may be allocated first to UEs with a high priority, and those UEs being allocated resources may be allowed to send and receive data to and from the base station or other UEs during the corresponding TTI.
Commonly used scheduling algorithms for radio resource allocation may include: round robin (RR), maximum carrier to interference (Max C/I), and proportional fair (PF). In the RR scheme, resources are allocated in sequence to UEs and services managed by the base station, heightening fairness. In the Max C/I scheme, resources are allocated first to a UE with the best channel condition, heightening overall throughput. The PF scheme tries to enhance both fairness and throughput by making good use of the strengths of the RR and Max C/I schemes.
The PF scheme aims to maximize the long-term throughput of a UE with a good channel condition relative to the average throughput. A scheduling priority for a UE may be computed by dividing the maximum throughput or peak throughput by the average throughput in the current channel condition. Proportional fair scheduling may be implemented in various ways according to communication systems or designs.
In PF scheduling, for a UE, the scheduling priority may be computed based on the maximum throughput in the current channel condition identified using channel quality information. In this case, those UEs that have the same channel quality but have different physical layer capabilities may have the same scheduling priority.
Generally, as a UE having a high physical layer capability is of a high price and has a high level, it has a high maximum throughput. In the case of resource allocation to UEs with different levels, when scheduling is performed based solely on channel quality information of each UE although overall channel conditions are acceptable, a UE having a high maximum throughput may miss an additional scheduling opportunity. In particular, when overall channel conditions are acceptable and UEs with different levels compete with each other, it is highly probable that the overall throughput of the base station is lowered.